Abstract: A portable thermosyphon water heating system for use by outdoor enthusiasts, or others at locations remote from a conventional supply of hot water. Water is heated by an open campfire flame in an enclosed heat exchanger, and is circulated between the heat exchanger and a portable non-pressurized reservoir by thermosyphon action. The hot water returning to the reservoir is discharged through a floating transfer conduit assembly, so the discharge rises and falls with the water level in the reservoir. The floating nature of the hot water return allows the majority of water within the reservoir to be used before refilling is needed, while maintaining thermosyphon action. A method of heating a liquid using the system described above is also provided, along with a retrofit apparatus for retrofitting existing reservoirs to use the thermosyphon principles and components of the present invention.